1. Field of the Invention
The present invention relates to a front derailleur for a bicycle, and more particularly to a front derailleur including a guide plate member movable by a shifting operation along a rotational axis of a front sprocket assembly to push a bicycle chain and shift the chain among three, large, intermediate and small, sprockets.
2. Description of the Related Art
In the above front derailleur, a chain trouble has often been encountered when the chain is shifted from the small sprocket to the large sprocket, the two sprockets having a great difference in diameter therebetween. That is, the front sprocket assembly often becomes unrotatable with the chain arrested between the large sprocket and an inner guide plate of the front derailleur. U.S. Pat. No. 4,078,444 discloses a solution to this problem, which provides an additional, auxiliary plate for contacting the chain. This auxiliary plate is attached to the inner guide plate to be elastically displaceable axially of the sprocket assembly. However, this prior construction has the disadvantages that the material for forming the auxiliary plate requires a drawing process, and that an irksome operation is involved in attaching the auxiliary plate to the inner guide plate.